Allyson Tighe 23 January 2012

Tattoos: they're not just for pirates and biker gangs any more. Beyonce has one, Joel Madden of Good Charlotte has tons, and so does Justin Timberlake - it seems like they're everywhere these days. Tattooing has become a pretty mainstream pastime; there are even reality shows on TV about tattoo shops.

Did you know? The word tattoo comes from the Tahitian word tatau, meaning "to mark"

Nobody really knows for sure when tattooing started, but there have been mummies found from 3000 B.C. with markings on their skin that could be early forms of tattoos. Tattoos were used in Japan and the South Pacific as tribal markings and symbols of honour, and came into popularity in the west in the late 17th century.

With the huge upswing in the popularity of tattoos seen today, the only logical next step, of course, is to look at the cool science behind them.

When tattoos were first used, they were generally done with ink derived from plants and animals. The process usually involved puncturing the skin with some sort of crude implement and putting the ink or dye in the wound. It sounds gross, but today's tattoo machines (sometimes called guns), do basically the same thing, just in a higher-tech kind of way.

Did you know? Some Arctic and Sub-Arctic tribes use to create tattoos by pulling a thread coated with soot thorough the skin.

The modern tattoo gun was modified from an engraving machine invented by Thomas Edison. It eventually evolved into what we see in the shops today: a 2-coiled electromagnetically powered machine. These machines have: a frame made out of conductive metal, a sterilized needle, a tube system for the ink, an electric motor, wire coils, and a foot pedal to control the speed of the needle.

The puncturing motion of the needle is controlled by electromagnetism — the phenomenon by which a magnetic field is produced by an electric current. Here's how it works:

When electricity enters the gun, a current runs through the frame to the contact spring, and through the coils to the contact screw. The circuit is completed where the contact screw meets the contact spring.

The completion of the circuit causes the coils to become magnetized, meaning the electrons in the coils become polarized and develop a north and south pole, just like in regular bar magnets. The reason the wires are coiled in this system so they can concentrate and increase the strength of the magnetic field.

This magnetism then pulls down on the bar above the coils, compressing the coil. The needle is attached to this bar, so as the bar moves down towards the coils, the needle moves down to puncture the skin.

However, as the bar is pulled down by the magnetic force, the contact screw is separated from the contact spring, causing the circuit to be broken. This causes the coils to become demagnetized.

The spring can then exert its upward force on the bar, allowing the bar to return to its original position and bringing the needle up with it as it goes. The contact spring and screw are then re-joined to complete the circuit. This magnetizes the coils, allowing the cycle to start again.

Did you know? The type of alternating electromagnetic switch used in tattoo guns is also found in doorbell buzzers. This cycle repeats itself 80-150 times per second, depositing the ink about 1mm below the surface of the skin.

Wrap a wire around a nail and attach one end of the wire to the top of a battery and the other end to the bottom of a battery. By doing so, you are sending an electrical current through the wire, causing the nail to become magnetized. You can verify that by picking up small objects or by showing its effect on a compass.

Thumbnail photo credit: Maria Kaloudi

Allyson did her B.Sc. in Genetics at the University of Western Ontario (UWO), and is currently working on her Master's in Physiology, also at UWO. Her work focuses on spinal cord injury and scar formation, and how to make the cells that make up that scar (astrocytes) more hospitable to nerve regeneration. Allyson is also learning whitewater kayaking, although most of her time is currently spent underwater and inhaling a lot of water at the moment.

Allyson Tighe

I completed my BSc and MSc at The University of Western Ontario, and am now a scientific writer and editorial assistant in Toronto. I am an expert risotto maker, a decidedly non-expert runner, and a WeatherNetwork junkie.